The present invention relates to motors, and particularly to a DC brushless motor with strong structure so that rotary shaft of the rotor can be firmly secured.
In the prior art, the DC (direct current) brushless motor is vertically arranged. Referring to FIG. 1, a prior art brushless motor is illustrated, where the motor includes a stator 10, a rotary shaft 21, cover 13, a casing 14 having a ventilating groove 140, and a fan 3. The stator 30 is formed by silicon steel sheets 11 and coils which are disposed in the cover 13. The rotor 20 is formed by a rotary shaft 21, a disk magnet 23 and an enhancing plate 25 having ventilating grooves 24, 26. The cover 13 has a groove seat 330. The seat has an axial hole. A bearing 15 is installed in the groove for assembling the rotary shaft 41. The casing 14 has a bearing 15 for locating the rotary shaft 21. The fan 3 is installed to the casing 14 at an upper end of the rotary shaft 21. However, above mentioned prior art has the following defects.
Only one bearing 15 is used to combine the rotary shaft 21 of the rotor 20 to the cover 13, so that ail the weight of the rotary shaft 21 is applied to the bearing 15. Thus the lifetime of the bearing is short and thus the bearing 15 is updated frequently. Moreover, the rotary shaft 21 easily shifts so as to generate noise.
Moreover, the enhancing plate 25 of the rotor 20 is combined to the magnet 23 in a plane configuration by glue agent. If the glue agent is deteriorated, the combination will become loose. Furthermore, the fan is made by plastically injection molding and then the fan is locked to the rotary shaft 21. Since plastic is soft, as the fan rotates with a higher speed, a large noise generates. Moreover, a gap is formed between the fan 3 the magnet 23 and the enhancing plate 25. No vortex generates on the enhancing plate 25. As a result, the air ventilation is low and heat dissipating is not preferred.
Accordingly, the primary object of the present invention is to provide a DC brushless motor which comprises a stator; a casing; a rotor formed by an enhancing plate, a magnet and a rotary shaft. The magnet and the enhancing plate are locked by studs other than using glue agent. A block on the lower surface of the enhancing plate is embedded into a central hole of the magnet so as to support the magnet and cause that the rotary shaft will not contact the magnet directly. A cover is extended with an inner sleeve. A groove seat is installed with a lower bearing and the inner sleeve is installed with a middle bearing and an upper bearing. The bearings are installed with respective enhancing pads. The rotary shaft of the rotor is installed with an annular enhancing flange and an annular inner flange which resist against the upper bearing. The inner flange resists against the enhancing pads of the middle bearing.
The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing.